EP0661535A1 - Capteur d'ions - Google Patents

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Publication number
EP0661535A1
EP0661535A1 EP94119430A EP94119430A EP0661535A1 EP 0661535 A1 EP0661535 A1 EP 0661535A1 EP 94119430 A EP94119430 A EP 94119430A EP 94119430 A EP94119430 A EP 94119430A EP 0661535 A1 EP0661535 A1 EP 0661535A1
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EP
European Patent Office
Prior art keywords
ion
water
electrode
metal
chloride
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EP94119430A
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German (de)
English (en)
Inventor
Koutarou Yamashita
Mamoru Taki
Yuji Miyahara
Toshiko Fujii
Satoshi Ozawa
Yoshio Watanabe
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Hitachi Ltd
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Hitachi Ltd
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Priority claimed from JP5315080A external-priority patent/JPH07167825A/ja
Priority claimed from JP5315081A external-priority patent/JPH07167826A/ja
Application filed by Hitachi Ltd filed Critical Hitachi Ltd
Publication of EP0661535A1 publication Critical patent/EP0661535A1/fr
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/403—Cells and electrode assemblies
    • G01N27/414—Ion-sensitive or chemical field-effect transistors, i.e. ISFETS or CHEMFETS
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/28—Electrolytic cell components
    • G01N27/30—Electrodes, e.g. test electrodes; Half-cells
    • G01N27/333—Ion-selective electrodes or membranes
    • G01N27/3335—Ion-selective electrodes or membranes the membrane containing at least one organic component

Definitions

  • the present invention relates to an ion sensor suitable for analysis of ion species contained in a biological liquid, and more particularly to an ion sensor suitable for analysis of potassium ion, sodium ion, halide ion or carbonate ion by potentiometric determination.
  • the ion sensor can selectively determine concentrations of specific ion species in a solution and has been employed in various fields including concentration monitoring of specific ion species, water quality analysis, etc. Particularly in the medical field it is applied to quantitatively determine ion species in blood or biological liquids such as urine, etc., for example, chloride ions, potassium ions, etc. Since concentrations of specific ion species in a biological liquid are closely related to metabolic reactions of living bodies, hypertension symptom, kidney disorder, neurosis trouble, etc. are diagnosed by determining concentrations of specific ion species.
  • E E0 + 2.303(RT/ZF) log a
  • the activity a of ion species to be determined can be simply calculated from measurements of the level E.
  • R is a gas constant
  • T an absolute temperature
  • Z an ionic factor
  • F a Faraday constant
  • E0 a standard potential of the system.
  • an ion sensor comprises an internal solid electrode, an ion selective membrane, an internal solution, where an agar gel containing a supporting electrolyte is used as the inner solution serving to conduct electricity between the ion-selective membrane and the inner electrode.
  • an ion sensor in such a structure that the ion selective membrane is directly provided on the internal solid electrode without using any internal solution is called coated wire electrode (CWE).
  • CWE coated wire electrode
  • Ion sensor disclosed in US Patent No. 4,214,968 can directly read concentrations of specific ion species as a function of ion activity by spotting a liquid sample without any preparative adjustment, storage by wet process or equilibration.
  • the above-mentioned CWE generally comprises an ion selective membrane, an internal solid electrode and an electrode body. Since the internal solid electrode is in direct contact with the ion selective membrane, the electrode potential level drifts largely and the electrode potential stability is not satisfactory when used for a prolonged time. Furthermore, the electrode resistance is high and CWE is highly susceptible particularly to changes in temperature.
  • An object of the present invention is to provide an ion sensor with practically prolonged maintenance of properties of electrode, freed from the above-mentioned problems of prior art.
  • an ion sensor which comprises an ion selective membrane (4a in Fig. 1), an internal solid electrode (2a in Fig. 1), a lead wire (11a in Fig. 1), a liquid sample path (5 in Fig. 1) and an electrode body (1 in Fig. 1), where an intermediate layer (3a in Fig. 1) is provided between the internal solid electrode and the ion selective membrane whose supporting membrane is composed of a hydrophobic polymer.
  • the intermediate layer comprises a hydrophilic polymer and an inorganic compound having a water-keeping property or an organic compound having a water-keeping property.
  • the intermediate layer comprises a hydrophilic polymer and one of pyridine, pyridazine, pyrazine, s-triazine, quinoline, isoquinoline, quinoxaline, acridine and a derivative thereof, or a hydrazine derivative represented by the following chemical formula: where R and R' are hydrogen atoms, alkyl groups or hydrokyl groups and n ⁇ 1.
  • the present ion sensor having an ion selectivity comprises an internal solid electrode of metal/metal salt composed of an electroconductive layer of at least one metal and a layer of an insoluble salt of the metal in contact with the electroconductive layer, an ion selective membrane whose supporting membrane is composed of a hydrophobic polymer, and an intermediate layer capable of keeping water molecules provided between the internal solid electrode and the ion selective membrane, the intermediate layer being composed of dried residues of an aqueous solution of an inorganic compound having a water-keeping property, or an organic compound having a water-keeping property, a hydrophilic polymer and an inorganic salt, where the organic compound is selected from the group consisting of polymethylene glycol, polyethylene glycol and polypropylene glycol, each having a molecular weight of 200 to 600, and the inorganic compound is selected from the group consisting of calcium chloride, gold chloride, magnesium perchlorate, magnesium fluoride, and vanadium chloride dioxide.
  • a plurality of the present ion sensors are provided along the path through which a liquid sample is made to flow, and the individual ion selective membranes of the ion sensors are brought into contact with the liquid sample to measure a plurality of ion species.
  • an equilibrium potential is generally developed at the interface between the ion selective membrane whose supporting membrane is composed of a hydrophobic polymer and the internal solid electrode. It seems that the equilibrium potential is generated mainly due to such a phenomenon that ionized metal ions from the internal solid electrode reach a distribution equilibrium at the interface between the hydrophobic ion selective membrane and the internal solid electrode. In the conventional ion sensor no satisfactory ionization takes place at the interface, and thus the distribution equilibrium is hardly reached.
  • the inorganic or organic compound having a water-keeping property used in the first mode of the present invention combines with water molecules on the basis of electrostatic interaction, thereby promoting ionic dissociation of inorganic salts from the intermediate layer due to the action of water molecules.
  • the compound used in the second mode of the present invention promotes ionization of the metal of the internal solid electrode on the basis of electrostatic interaction.
  • metal ions generated mostly by ionization of the metal of the internal solid electrode can rapidly reach at the interface between the ion selective membrane and the internal solid electrode, and thus an ion sensor with practically prolonged maintenance of properties of electrode can be provided. That is, liquid samples can be measured with a stable accuracy for a prolonged time in a path through which the liquid samples flow.
  • the present invention provides an ion sensor capable of serving for a prolonged time with an improved accuracy and a higher reliability.
  • Fig. 1 is a vertical cross-sectional view showing the structure of a single ion sensor according to one embodiment of the present invention.
  • Fig. 2 is a vertical cross-sectional view showing the structure of an assembly of a plurality of ion sensors for measuring concentrations of a plurality of ion species according to another embodiment.
  • Fig. 3 is a vertical cross-sectional view showing the structure of an ion selective field effect transistor according to other embodiment of the present invention.
  • Fig. 4 is a diagram showing changes in the electrode potential level ion sensors in time course according to embodiments of the present invention and the conventional ion sensor.
  • Fig. 5 is a diagram showing changes in the electrode potential level drift of ion sensors in time course according to other embodiments of the present invention and the conventional ion sensor.
  • Fig. 6 is a diagram showing changes in the electrode potential level of ion sensors in time course according to further embodiments of the present invention and the conventional ion sensor.
  • Fig. 7 is a diagram showing changes in the electrode potential level of ion sensors in time course according to still further embodiments of the present invention and the conventional ion sensor.
  • Figs. 8 to 11 are diagrams showing changes in the electrode resistance of ion sensors in time course according to still further embodiments of the present invention.
  • water-keeping property of a compound herein used means an ability of the compound to positively keep water molecules. That is, electrostatic bonding or some other bonding is established between the compound and water molecules on the basis of chemical or physical actions, and such a bonding can be maintained for a prolonged time.
  • Hydrophilic polymer for the intermediate layer is selected from the group consisting of poly(vinyl alcohol), polyethylene oxide, polypropylene oxide, polyacrylic acid salt, polymethacrylic acid salt, polystyrene acid salt, carboxylmethyl cellulose and a derivative thereof.
  • Compounds having a water-keeping property include deliquescent solids. Daliquescency appears mostly in inorganic compounds when the water vapor pressure of an aqueous saturated solution of a solid is lower than the partial pressure of water vapor in the air in contact with the aqueous saturated solution. In inorganic compounds, water molecules exist as water of crystallization. Water of crystallization is the water contained in a specific combination ratio in the crystal and includes coordination water, lattice water, structure water, etc.
  • Preferable inorganic compounds having a water-keeping property for use in the present invention include, for example, calcium chloride, gold chloride, magnesium perchlorate, sodium perchlorate, germanium fluoride and vanadium chloride dioxide.
  • the following inorganic compounds can be used in the present invention: silver perchlorate, aluminum chloride, aluminum iodide, boron triiodide, barium perchlorate, barium nitrate, beryllium chloride, bismuth chloride, calcium bromide, calcium iodide, cerium chloride, cobalt bromide, cesium chloride, iron bromide, iron iodide, gallium chloride, germanium iodide, iodine trichloride, indium chloride, iridium chloride, potassium sulfide, potassium selenite, potassium nitrite, potassium acetate, lanthanum chloride, lithium chloride, lithium chlorate, magnesium chloride, manganese chloride, silver
  • Organic compounds having a water-keeping property are those containing nitrogen, oxygen, phosphorus, sulfur, halogen, etc. therein and capable of forming hydrogen bonds with water molecules.
  • Preferable organic compound having a water-keeping property include, for example, ethylene glycol, glycerol, N,N-dimethylhydrazine, 2-aminoethanol, 2-cyanopropionic acid and phenol-2,4-disulfonic acid.
  • organic compounds can be used in the present invention: 2-bromoethanol, promazine hydrochloride, 2-naphthol-3,6-disulfonic acid, tropine, thiopental sodium, diethyl (R,R)-tantrate, trimethylamine oxide, N,N'-dimethylhydrazine, N,N'-dimethylthiourea, dimethylamine hydrochloride, ammonium acetate, methylhydrazine, N-methylhydroxylamine, 3-methoxy-1,2-propanediol and 4-amino-1,2,4-triazole.
  • Ion selective membrane can select a specific ion species. That is, it can selectively penetrate or induce only a specic ion species therethrough from a liquid sample also containing other ion species not destined for the measurement.
  • the ion selective membrane must be water-insoluble, because a liquid sample is an aqueous solution, and can be either hydrophilic or hydrophobic so long as it is water-insoluble.
  • Such an ion selective membrane can be prepared in a known manner, for example, by dissolving an ion carrier and an organic binder into a solvent, applying the resulting solution to the surface of a water-insoluble salt layer, an electrolyte layer or a conductive layer, followed by drying.
  • An ion carrier concentration is generally 0.05 to 10 g/m2
  • the thickness of ion selective membrane is preferably 10 to 500 ⁇ m.
  • Organic binder for use in the ion selective membrane can be natural or synthetic polymers capable of forming a thin film having a sufficient ion penetrability and an ion mobility together with an ionophore or an ionophore solvent and includes, for example, such known materials as poly(vinyl chloride), poly(vinyl alcohol), poly(vinylidone chloride), etc.
  • Ion carrier for use in the ion selective membrane can be substances capable of forming pairs with a desired specific alkali metal ion species, alkaline earth metal ion species, etc.
  • potassium ion carrier such well known substances as valinomycin, cyclic polyether, etc.
  • sodium ion carrier such well known substances as monesin sodium, methylmonesin, etc.
  • materials for the ion selective membrane such well known ion-exchangeable materials as quaternary borate, quaternary ammonium salts, etc. can be used.
  • the carrier solvent is sufficiently water-insoluble and non-volatile.
  • Such well known substances as phthalate, sebacates, aromatic or aliphatic ethers, adipates, etc. are desirable ones.
  • the internal solid electrode is in such a structure that a metal is in contact with its insoluble salt, and can be shown by metal/metal salt, for example, by Ag/AgX, where X is a halogen such as Cl, Br, I, etc, which can be prepared by dipping a silver layer as a wire or plate into an aqueous solution of a halogen salt.
  • metal/metal salt for example, by Ag/AgX, where X is a halogen such as Cl, Br, I, etc, which can be prepared by dipping a silver layer as a wire or plate into an aqueous solution of a halogen salt.
  • a halogen salt such as Cl, Br, I, etc
  • an insoluble salt tetraphenylborate, tetraalkylborate or their derivative metal salts can be used.
  • total thickness of the metal layer and the metal salt layer in the layer structure of metal/metal salt is not more than 500 ⁇ m and the thickness of the metal salt layer is 10 to 50% of that of the metal layer. It is not necessary that the entire surface of the metal layer is completely covered by the metal salt layer. That is, not more than 50% of the surface of the metal layer is preferably covered by the metal salt layer.
  • organic compounds having a water-keeping property are water-soluble and non-decomposable, and also that organic compounds having a water-keeping property are water-soluble and non-decomposable and have a low volatility.
  • Particularly useful organic compounds are poly(alkylene oxide) having a molecular weight of 200 to 600, represented by the following chemical formula: HO[(CH2) n O] m H, where m and n ⁇ 1, such as polyethyleneglycol, polymethyleneglycol, polypropyleneglycol, etc. having a vapor pressure of not more than 0.001 mm Hg (100°C).
  • These organic compounds have particularly a low volatility and thus a stable property of electrode can be maintained for a prolonged time.
  • This example shows use of various organic compounds of low molecular weight having a water-keeping property and silver/silver chloride as an internal solid electrode.
  • Fig. 1 is a vertical cross-sectional view showing the structure of an ion sensor according to one embodiment of the present invention, where an ion selective membrane 4a is fixed along a liquid sample path 5 at the central position of an electrode body 1 and an intermediate layer 3a is sandwiched between an internal solid electrode 2a of silver/silver chloride and the ion selective membrane 4a, and a lead wire 11a is connected to the internal solid electrode 2a through the electrode body 1.
  • a voltage of about 0.7 V was applied between a concentrated nitric acid-treated silver plate (0.2 mm thick; 10 mm x 10 mm square), as a positive electrode and a platinum wire (0.5 mm in diameter; 50 mm long) as a negative electrode for about 30 minutes in an aqueous 1 mM sodium chloride solution.
  • the positive electrode was washed with water and dried, whereby a silver/silver chloride (Ag/AgCl) internal solid electrode was obtained.
  • the thus prepared electrode was connected to an external reference electrode through a salt bridge of saturated KCl, and subjected to potentiometry between the external reference electrode and the electrode, using an aqueous 100 mM potassium chloride solution as a test solution. Results of evaluation are given in Table 1.
  • the entire electric battery for the potentiometry has the following general structure: Ag/AgCl/saturated KCl/test solution as sample solution/ion selective membrane/PVA-KCl-water-keeping material/AgX/Ag, where X is Cl.
  • Electrode sensitivity to potassium ions was found to be about 56 to about 58 mV/dec. throughout all the test numbers, and the electrode resistance of the electrode without the water-keeping material (Test No. 7) was found to be 215 M ⁇ , whereas those of the electrodes with the water-keeping materials (Test Nos. 1 to 6) were found to be about a half to smaller fractions of that of Test No. 7. Decrease in the electrode resistance of the electrode with glycerol having a low volatility (Test No. 2) was particularly remarkable.
  • This example shows use of various organic compounds (polymer compounds) having a water-keeping property and silver/silver chloride as an internal solid electrode.
  • Example 9 electrodes were prepared in the same manner as in Example 1, except that the organic compounds having a water-keeping property of Example 1 were replaced with polymeric compounds as shown in Table 2 as Test Nos. 1 to 9, where polymethylene glycol (PMG), polyethylene glycol (PEG) and polypropylene glycol (PPG) each having molecular weights of 200, 400 and 600 were used.
  • PMG polymethylene glycol
  • PEG polyethylene glycol
  • PPG polypropylene glycol
  • Electrode sensitivity (mV/dec.) Electrode resistance (M ⁇ ) 1 PMG-200 56.9 21 2 PMG-400 56.2 22 3 PMG-600 57.5 19 4 PEG-200 57.6 18 5 PEG-400 56.1 22 6 PEG-600 57.2 18 7 PPG-200 58.0 23 8 PPG-400 57.3 19 9 PPG-600 56.6 18 10 None 56.5 215
  • Electrode sensitivity to potassium ions was found to be about 56 to about 58 mV/dec throughout all the test numbers, as in Example 1, and the electrode resistance of the electrode without the water-keeping material (Test No. 10) was found to be 215 MG, whereas those of the electrodes with the water-keeping materials (Test Nos. 1 to 9) were found to be about one-tenth of that of Test No. 10. It seems that the polymeric compounds having a larger molecular weight have a particularly lower electrode resistance because of lower volatility.
  • This example shows use of polyethylene glycol at various concentrations as a water-keeping material and silver/silver chloride as an internal solid electrode.
  • Silver/silver chloride internal solid electrodes were prepared in the same manner as in Example 1. Then, about 10 ⁇ l of one of aqueous 5mM KCl solutions prepared by adding 100 mg of polyvinyl alcohol (PVA), 100 mg of potassium chloride (KCl) and polyethylene glycol (PEG) having a molecular weight of 600 in one of ratios of PEG to PVA by weight of 0.1, 0.5, 1.0, 2.0, 5.0 and 10.0 to 1 l of water was dropwise applied to the AgCl surface of silver/silver chloride (Ag/AgCl) internal solid electrode and dried for about one day to form an intermediate layer on the electrode.
  • PVA polyvinyl alcohol
  • KCl potassium chloride
  • PEG polyethylene glycol
  • Electrode sensitivity to potassium ions was found to be about 56 to about 58 mM/dec throughout all the test numbers, as in Example 1, and the electrode resistance of electrode without PEG (Test No. 7) was found to be 215 M ⁇ , whereas that of electrode with PEG in a ratio of 0.1 by weight (Test No. 1) was found to be as low as about 50 M ⁇ , and those of other electrodes with PEG in other ratios (Test Nos. 2 to 6) were found to be 21 M ⁇ or less, which was about one-tenth of that of Test No. 7.
  • Sodium ion selective electrodes and chloride ion selective electrodes could be prepared in the same manner as in Example 1, except that potassium chloride (KCl) was replaced with sodium chloride (NaCl) and sodium ion selective membranes and chloride ion selective membranes were used as ion selective membranes, and it was found that they could have similar properties of electrode to those of the potassium ion selective electrodes.
  • KCl potassium chloride
  • This example shows use of polyethylene glycol at various concentrations as a water-keeping material and silver/silver bromide as internal solid electrodes.
  • Potassium ion selective electrodes were prepared in the same manner as in Example 3 by changing the internal solid electrodes of Example 3 to silver/silver bromide (Ag/AgBr) electrodes, preparing intermediate layers having the same compositions in Example 3 and pasting the surfaces of the intermediate layers with the same ion selective membrane as in Example 1 and subjected to the same potentiometry as in Example 1. Results of evaluation are shown in Table 4. Table 4 Test No. Ratio of PEG to PVA by weight Electrode sensitivity (mV/dec.) Electrode resistance (M ⁇ ) 1 0.1 57.3 21 2 0.5 57.6 21 3 1.0 56.3 19 4 2.0 57.8 18 5 5.0 57.1 18 6 10.0 58.2 17 7 0 56.5 215
  • Electrode sensitivity to potassium ions was found to be about 56 to about 59 mV/dec throughout all the test numbers, and electrode resistance of electrode without PEG (Test No. 7) was found to be 215 M ⁇ , whereas those of electrodes with PEG in various ratios (Test Nos. 1 to 6) were found to be 21 M ⁇ or less, which was about one-fourth of that of Test No. 7. Judging only from the electrode resistance, silver/silver bromide (Ag/AgBr) is better as internal solid electrode materials than silver/silver chloride (Ag/AgCl).
  • This example shows use of various inorganic compounds having a water-keeping property and silver/silver chloride as internal solid electrodes.
  • Potassium ion selective electrodes were prepared in the same manner as in Example 1 except that the water-keeping materials were replaced with inorganic compounds i.e. calcium chloride (CaCl2 ⁇ (H2O), gold chloride (AuCl3 ⁇ 2H2O), magnesium perchlorate (Mg (ClO4)2 ⁇ 8H2O), sodium perchlorate (NaClO4 ⁇ (H2O), germanium fluoride (GeF2), and vanadium chloride dioxide (VClO2), while using the same intermediate layer composition as used in Example 1 and then pasting the surfaces of the intermediate layers with the same ion selective membrane as used in Example 1, and then subjected to the same potentiometry as in Example 1. Results of evaluation are shown in Table 5.
  • inorganic compounds i.e. calcium chloride (CaCl2 ⁇ (H2O), gold chloride (AuCl3 ⁇ 2H2O), magnesium perchlorate (Mg (ClO4)2 ⁇ 8H2O), sodium perch
  • Electrode sensitivity mV/dec.
  • Electrode resistance M ⁇ 1 Calcium chloride 57.2 22 2 Gold chloride 57.6 23 3
  • Magnesium perchlorate 57.3 18 4
  • Sodium perchlorate 56.8 20 5
  • Germanium fluoride 57.9 18 6 Vanadium chloride dioxide 57.2 20 7 None 56.8 215
  • Electrode sensitivity to potassium ions was found to be about 56 to about 58 mV/dec throughout all the test numbers, as in Example 1, and the electrode resistance without any water-keeping material (Test No. 7) was found to be 215 M ⁇ , whereas those of electrodes with the water-keeping materials (Test Nos. 1 to 6) were found to be about one-tenth of that of Test No. 7.
  • This example shows use of calcium chloride having a water-keeping property at various concentrations and silver/silver chloride as an internal solid electrode.
  • Potassium ion selective electrodes were prepared in the same manner as in Example 5, except that the water-keeping material was fixed to calcium chloride (CaCl2 ⁇ 1H2O) and intermediate layers were formed in various ratios of calcium chloride to PVA by weight, i.e. 0.1, 0.5, 1.0, 2.0, 5.0 and 10.0. The surfaces of intermediate layers were then pasted with the same ion selective membrane as used in Example 1. The potassium ion selective electrodes were subjected to the same potentiometry as in Example 1. Results of evaluation are shown in Table 6. Table 6 Test No.
  • Electrode sensitivity mV/dec.
  • Electrode resistance M ⁇ 1 0.1 56.3 62 2 0.5 56.6 43 3 1.0 56.5 21 4 2.0 58.8 19 5 5.0 57.9 17 6 10.0 58.2 17 7 0 56.5 215
  • Electrode sensitivity to potassium ions was found to be about 56 to about 59 mV/dec throughout all the test numbers, and the electrode resistance of electrode without the water-keeping material (Test No. 7) was found to be 215 M ⁇ , whereas those of electrodes in ratios of 0.1 and 0.5 by weight (Test Nos. 1 and 2) were found to be as low as about 60 M ⁇ and about 40 M ⁇ , respectively, and those of other electrodes (Test Nos. 3 to 6) were found to be 21 M ⁇ or less, which were about one-tenth of that of Test No. 7.
  • This example shows use of calcium chloride having a water-keeping property at various concentrations and silver/silver bromide as an internal solid electrode.
  • Potassium ion selective electrodes were prepared in the same manner as in Example 6 except that the internal solid electrode was replaced with silver/silver bromide (Ag/AgBr). The same intermediate layer as disclosed in Example 6 was provided on each of the internal solid electrodes and then pasted with the same ion selective membrane as disclosed in Example 1 on the surface. The thus prepared potassium ion selective electrodes were subjected to the same potentiometry as in Example 1. Results of evaluation are shown in Table 7. Table 7 Test No.
  • Electrode sensitivity mV/dec.
  • Electrode resistance M ⁇ 1 0.1 57.3 22 2 0.5 56.8 23 3 1.0 57.5 20 4 2.0 57.8 18 5 5.0 57.0 17 6 10.0 57.2 18 7 0 56.5 215
  • Electrode sensibility to potassium ions was found to be about 56 to about 58 mV/dec throughout all the test numbers, as in Example 1, and the electrode resistance of electrode without the water-keeping material (Test No. 7) was found to be 215 M ⁇ , whereas those of electrodes with the water-keeping material (Test Nos. 1 to 6) were found to be 23 M ⁇ or less, which was about one-tenth of that of Test No. 7. It was found that silver/silver bromide (Ag/AgBr) was better as internal solid electrode materials than silver/silver chloride (Ag/AgCl), as in Example 4.
  • This example shows use of polyethylene glycol at a constant concentration and calcium chloride at various concentration as water-keeping materials, and silver/silver chloride as an internal solid electrode.
  • Potassium ion selective electrodes were prepared in the same manner as in Example 6, except that polyethylene glycol (PEG) having a molecular weight of 600 and calcium chloride (CaCl2 ⁇ 1H2O) were used as water-keeping materials, where a ratio of PEG to PVA by weight was set to 1.0, whereas that of calcium chloride to PVA was 0.1, 0.5, 1.0, 2.0, 5.0 and 10.0.
  • PEG polyethylene glycol
  • CaCl2 ⁇ 1H2O calcium chloride
  • Electrode sensitivity mV/dec.
  • Electrode resistance M ⁇
  • PEG600 CaCl2 1 1.0 0.1 56.4 22 2 1.0 0.5 57.6 23 3 1.0 1.0 58.5 20 4 1.0 2.0 57.8 19 5 1.0 5.0 57.1 18 6 1.0 10.0 58.1 17 7 0 0 56.5 215
  • Electrode sensitivity to potassium ions was found to be about 56 to about 59 mV/dec throughout all the test numbers, and the electrode resistance of the electrode without the water-keeping materials (Test No. 7) was found to be 215 M ⁇ , whereas those of electrodes with the water-keeping materials (Test Nos. 1 to 6) were found to be 23 M ⁇ or less, which was about one-tenth of that of Test No. 7.
  • This example shows use of polyethylene glycol at a constant concentration and calcium chloride at various concentrations as water-keeping materials and silver/silver bromide as an internal solid electrode.
  • Potassium ion selective electrodes were prepared in the same manner as in Example 8, except that the internal solid electrode was replaced with silver/silver bromide (Ag/AgBr). Intermediate layers having the same compositions as in Example 8 on the internal solid electrodes were pasted with the same ion selective membrane as disclosed in Example 1. The thus prepared potassium ion selective electrodes were subjected to the same potentiometry as disclosed in Example 1. Results of evaluation are shown in Table 9. Table 9 Test No.
  • Electrode sensitivity mV/dec.
  • Electrode resistance M ⁇
  • PEG600 CaCl2 1 1.0 0.1 56.6 19 2 1.0 0.5 57.9 20 3 1.0 1.0 58.0 21 4 1.0 2.0 57.2 19 5 1.0 5.0 58.1 18 6 1.0 10.0 57.1 18 7 0 0 56.5 215
  • Electrode sensitivity to potassium ions was found to be about 56 to about 59 mV/dec. throughout all the test numbers, and the electrode resistance of the electrode without the water-keeping material (Test No. 7) was found to be 215 M ⁇ , whereas those of electrodes with the water-keeping materials (Test Nos. 1 to 6) were found to be 21 M ⁇ or less, which was about one-tenth of that of Test No. 7.
  • This example shows evaluation of measurement accuracy when polyethylene glycol was used as a water-keeping material and silver/silver chloride was used as an internal solid electrode.
  • Potassium ion selective electrodes were prepared in the same manner as in Example 1, except that potassium chloride was replaced with polyethylene glycol (PEG) having a molecular weight of 600 as a water-keeping material for the intermediate layer, and subjected to measurement of potassium ion concentration in aqueous potassium chloride solutions having different potassium ion concentrations as test solutions (Test Nos. 1 to 3) to evaluate measurement accuracy and reproducibility. Results of evaluation are shown in Table 10. Table 10 Test No. Potassium ion concentration (mM) Number of measurements CV (%) as prepared Average of measurements 1 1.5 1.49 20 0.22 2 2.0 2.02 20 0.31 3 3.0 3.01 20 0.16
  • This example shows evaluation of measurement accuracy when calcium chloride was used as a water-keeping material and silver/silver chloride was used as an internal solid electrode.
  • Potassium ion selective electrodes were prepared in the same manner as in Example 1, except that potassium chloride was replaced with calcium chloride (CaCl2 ⁇ 1H2O) as a water-keeping material for the intermediate layer, and subjected to measurement of potassium ion concentration in aqueous potassium chloride solutions having different potassium ion concentrations as test solutions (Test Nos. 1 to 3) to evaluate measurement accuracy and reproducibility. Results of evaluation are shown in Table 11. Table 11 Test No. Potassium ion concentration (mM) Number of measurements CV (%) as prepared Average of measurements 1 1.5 1.48 20 0.28 2 2.0 2.04 20 0.33 3 3.0 3.03 20 0.19
  • Fig. 2 is a vertical cross-sectional view showing the structure of an assembly of ion sensors for measuring concentrations of a plurality of ion species, which comprises internal solid electrodes 2a to 2c, intermediate layers 3a to 3c, ion selective membranes 4a to 4c and lead wires 11a to 11c. That is, a plurality of ion sensors are provided along a path through which a liquid sample flows and concentrations of a plurality of ion species are measured through contact of the individual ion selective membranes 4a to 4c of the ion sensors with a liquid sample.
  • This example shows use of an ion sensitive field effect transistor.
  • Fig. 3 is a vertical cross-sectional view showing the structure of a field effect transistor according to one embodiment of the present invention, where an n-type source 6 and an n-type drain 7 are formed on a silicon substrate 8, and covered with a SiO2 membrane 9 and a Si3N4 insulation membrane 10, successively, to prepare a field effect transistor.
  • a voltage of about 0.7 V was applied between a concentrated nitric acid-pretreated silver plate, 0.2 mm in thickness and 5 mm x 5 mm square, as a positive electrode and a platinum wire, 0.5 mm in diameter and 50 mm long, as a negative electrode in an aqueous 1 mM NaCl solution for about 30 minutes.
  • the positive electrode was washed with water and dried to obtain a silver/silver chloride internal solid electrode.
  • the silver/silver chloride electrode was provided onto the Si3N4 insulation membrane 10.
  • an intermediate layer 3 having one of compositions disclosed in the foregoing Examples 1 to 11 and the following Examples 29 to 32 was formed on the AgCl surface of the internal solid electrode.
  • KCl poly(vinyl alcohol)
  • PEG polyethylene glycol
  • the surface of the intermediate layer 3 was pasted with a potassium ion selective membrane 4 having the same composition as disclosed in Example 1 to prepare a potassium ion sensitive field effect transistor.
  • the thus prepared potassium ion sensitive field effect transistors were subjected to measurement of potassium ion concentrations in aqueous potassium chloride solutions having different potassium ion concentrations as test solutions (Test Nos. 1 to 3) to evaluate the measurement accuracy and reproducibility. Results of evaluation are shown in Table 12.
  • Sodium ion selective electrodes and chloride ion selective electrodes could be prepared in the same manner as in Example 12 by replacing potassium chloride (KCl) with sodium chloride (NaCl) as an inorganic salt constituent for the intermediate layer and using a sodium selective membrane and a chloride ion selective membrane, respectively, in place of the potassium ion selective membrane, and could have similar properties of electrode to those of the potassium ion selective electrodes.
  • KCl potassium chloride
  • NaCl sodium chloride
  • This example shows comparison of the present ion selective electrodes with a conventional electrode in changes in electrode potential level in time course.
  • Fig. 4 is a diagram showing changes in the electrode potential level in time course when the present ion selective electrodes and a conventional electrode were subjected as potassium ion measurement using an aqueous potassium chloride solution as a test solution, where electrode potential level values measured at every intervals of 2 hours were plotted for every ten hours.
  • curve (C) shows electrode potential level of the conventional electrode without any intermediate layer, which was prepared in the following manner: After first, a voltage of about 0.7 V was applied between a concentrated nitric acid-pretreated silver plate, 0.2 mm thick and 10 mm x 10 mm square, as a positive electrode and a platinum wire, 0.5 mm in diameter and 50 mm long, as a negative electrode in an aqueous 1 mM KCl solution for about 30 minutes. After the voltage application, the positive electrode was washed with water and dried to obtain silver/silver chloride (Ag/AgCl) as an internal solid electrode. The thus obtained silver/silver chloride internal solid electrode was then pasted with a potassium ion selective membrane having the same composition as in Example 1 (as shown by 4a in Fig. 1) to prepare a potassium ion selective electrode.
  • a voltage of about 0.7 V was applied between a concentrated nitric acid-pretreated silver plate, 0.2 mm thick and 10 mm x 10 mm
  • curve (a) shows electrode potential level of the present potassium ion selective electrode with an intermediate layer containing polyethylene glycol (PEG) having a molecular weight of 600 as a water-keeping material in a ratio of PEG to poly(vinyl alcohol) (PVA) of 1.0 by weight, as shown in Example 3, and curve (b) shows electrode potential level of the present potassium ion selective electrode with an intermediate layer containing calcium chloride (CaCl2 ⁇ 1H2O) as a water-keeping material in a ratio of calcium chloride to PVA of 1.0 by weight, as shown in Example 6.
  • PEG polyethylene glycol
  • PVA poly(vinyl alcohol)
  • This example shows comparison of the present ion selective electrodes with a conventional electrode in changes in drift of electrode potential level in time course.
  • Fig. 5 is a diagram showing changes in drift of electrode potential level in time course, when the present ion selective electrodes and a conventional electrode were subjected to potassium ion measurement using an aqueous potassium chloride solution as a test solution where from E(t) values, i.e. electrode potential level values measured at every intervals of 2 hours, a value of E(t+2) - E(t) was obtained as a drift, which was plotted for every 10 hours.
  • E(t) values i.e. electrode potential level values measured at every intervals of 2 hours
  • curve (c) shows changes in drift of electrode potential level of the conventional electrode without any intermediate layer, prepared in the same manner as in Example 13, in time course.
  • Course (a) shows changes in drift of electrode potential level of the present ion selective electrode with an intermediate layer containing polyethylene glycol (PEG) having a molecular weight of 600 as a water-keeping material in a ratio of PEG to poly(vinyl alcohol) (PVA) of 1.0 by weight, as shown in Example 3, in time curse and curve (b) shows changes in drift of electrode potential level of the present ion selective electrode with an intermediate layer containing calcium chloride (CaCl2 ⁇ 1H2O) as a water-keeping material in a ratio of calcium chloride to PVA of 1.0 by weight, as shown in Example 6, in time curse.
  • PEG polyethylene glycol
  • PVA poly(vinyl alcohol)
  • the present ion sensors are very practical, because good properties of electrode can be maintained for a prolonged time, as compared with the conventional one, and are particularly suitable for continuous measurement of liquid samples flowing along the path.
  • This example shows use of various cyclic compounds having at least one double bond and containing at least one nitrogen atom as water-keeping materials and of silver/silver chloride as an internal solid electrode.
  • a silver/silver chloride internal solid electrode was prepared in the same manner as in Example 1 and then pasted with a potassium ion selective membrane having the following composition to prepare a conventional potassium ion selective electrode.
  • the organic compounds herein used were 2,4-pyridinediol (Chemical Formula 1), 4-pyridinemethanol (Chemical Formula 2), pyridine-3-carboxylic acid (Chemical Formula 3) and pyridine-2,5-carboxylic acid diethyl ether.
  • an Ag/AgCl external reference electrode was connected with one of the thus prepared internal solid electrodes through a saturated KCl salt bridge to measure potential level differences between the external reference electrode and the internal solid electrode. That is, an electrode sensitivity, a potential level drift over 20 hours after the start of measurement and an electrode resistance were determined, using the same aqueous KCl solution as a test solution as in Example 1. Results of evaluation are given in Table 13, where Test Nos.
  • the entire battery for measuring a potential level difference with one of the potassium ion selective electrodes has the following structure: Ag/AgCl/saturated KCl/test solution as liquid sample/ion selective membrane/PVA-organic compound/AgX/Ag where X is Cl.
  • Composition of potassium ion selective membrane Valinomycin 0.1 g Poly(vinyl chloride) 2.0 g Didodecyl phthalate 0.01 g Table 13 Test No.
  • Electrode sensitivity to potassium ions was found to be about 56 to about 58 mV/dec. throughout all the test numbers including the conventional case, and electrode resistance of the conventional case was 250 M ⁇ , whereas those of Test Nos. 1 to 4 were found to be about one-tenth of that of the conventional case. It was also found that the potential level drift after 20 hours from the start of measurement of Test Nos. 1 to 4 was reduced to less than about one-fifth of that of the conventional case.
  • This example shows use of various cyclic compounds having at least one double bond and containing at least one nitrogen atom as water-keeping materials and silver/silver bromide as an internal solid electrode.
  • Potassium ion selective electrodes were prepared in the same manner as in Example 15 except that the internal solid electrode was replaced with Ag/AgBr. That is, the same intermediate layer, ion selective membrane, preparation and measurement procedures and evaluation items as in Example 15 were employed. Results of evaluation are shown in Table 14, where water-keeping compounds used in Test Nos. 1 to 4 correspond to those of Chemical Formulas 1 to 4, respectively. Table 14 Test No. Electrode sensitivity (mV/dec.) Potential level drift (mV/20 hr) Electrode resistance (M ⁇ ) 1 56.7 7.9 22 2 57.5 8.2 20 3 57.6 6.6 20 4 57.3 6.6 18 Conventional 57.1 56 120
  • Electrode sensitivity to potassium ions was found to be about 56 to about 58 mv/dec. throughout all the test numbers including the conventional case. It was found that the electrode resistivity of the conventional case was 120 M ⁇ , as in Example 15, whereas those of Test Nos. 1 to 4 were reduced to a few fractions of that of the conventional case. Potential level drift of Test Nos. 1 to 4 was reduced to less than one-fifth of that of the conventional case.
  • This example shows use of various cyclic compounds having at least one double bond and containing at least one nitrogen atom as water-keeping materials and silver/silver iodide as an internal solid electrode.
  • Potassium ion selective electrodes were prepared in the same manner as in Example 15, except that the internal solid electrode was replaced with Ag/AgI. That is, the same intermediate layer, ion selective membrane, preparation and measurement procedures and evaluation items as in Example 15 were employed. Results of evaluation were given in Table 15, where water-keeping compounds used in Test Nos. 1 to 4 correspond to those of Chemical Formulas 1 to 4, respectively. Table 15 Test No. Electrode sensitivity (mV/dec.) Potential level drift (mV/20 hr) Electrode resistance (M ⁇ ) 1 57.7 10.9 20 2 56.5 9.2 19 3 57.8 8.6 20 4 57.1 7.6 18 Conventional 57.0 51 105
  • Electrode sensitivity to potassium ions was found to be about 56 to about 58 mV/dec. throughout all the test numbers including the conventional case, as in Example 15. It was found that the electrode resistance of the conventional case was 105 M ⁇ , whereas those of Test Nos. 1 to 4 were reduced to a few fractions of that of the conventional case. Potential level drift was also found to be reduced to less than about one-fifth of that of the conventional case.
  • This example shows use of various cyclic compounds having at least one double bond and at least one nitrogen atom as water-keeping materials, an inorganic salt and silver/silver chloride as an internal solid electrode.
  • Potassium ion selective electrodes were prepared in the same manner as in Example 15, except that an intermediate layer was formed from an aqueous solution prepared by adding 100 mg of poly(vinyl alcohol) (PVA), 100 mg of a cyclic compound selected from those mentioned in Example 15 as Chemical Formulas 1 to 4 and 100 mg of potassium chloride to 1 l of water on the surface of the internal solid electrode, where the surface of the intermediate layer was pasted with a potassium ion selective membrane having the same composition as in Example 15.
  • PVA poly(vinyl alcohol)
  • the same evaluation items as in Example 15 were measured by potentiometry. Results of evaluation are shown in Table 16, where the water-keeping materials used in Test Nos. 1 to 4 correspond to those of Chemical Formulas 1 to 4.
  • the entire electric battery for the potentiometry had the following structure: Ag/AgCl/saturated KCl/test solution as liquid sample/ion selective membrane/PVA-inorganic salt-cyclic compound/AgX/Ag, where X is Cl.
  • Table 16 Test No. Electrode sensitivity (mV/dec.) Potential level drift (mV/20 hr) Electrode resistance (M ⁇ ) 1 56.7 8.9 21 2 57.0 10.3 21 3 56.1 8.6 19 4 57.9 8.5 19 Conventional 57.1 41 220
  • Electrode sensitivity to potassium ions was found to be about 56 to about 58 mV/dec. throughout all the test numbers including the conventional case, as in Example 15. It was found that the electrode resistance of the conventional case was 220 M ⁇ , whereas those of Test Nos. 1 to 4 were reduced to 2 M ⁇ or less, which was about one-tenth of that of the conventional case. Potential level drift was found to be reduced to about one-fourth of that of the conventional case.
  • This example shows use of various cyclic compounds having at least one double bond and containing at least one nitrogen atom as water-keeping materials, an inorganic salt and silver/silver bromide as an internal solid electrode.
  • Potassium ion selective electrodes were prepared in the same manner as in Example 18 except that the internal solid electrode was replaced with silver/silver bromide (Ag/AgBr). The same intermediate layer, ion selective membrane, preparation and measurement procedures and evaluation items as in Example 18 were employed. Results of evaluation are shown in Table 17, where the water-keeping materials used in Test Nos. 1 to 4 correspond to those of Chemical Formula 1 to 4, respectively. Table 17 Test No. Electrode sensitivity (mV/dec.) Potential level drift (mV/20 hr) Electrode resistance (M ⁇ ) 1 55.7 6.9 20 2 56.5 7.2 20 3 55.6 6.8 20 4 57.1 7.6 19 Conventional 56.1 35 110
  • Electrode sensitivity to potassium ions of Test Nos. 1 to 4 including the conventional case was found to be about 56 to about 58 mV/dec, as in Example 15. It was found that the electrode resistance of the conventional case was 110 M ⁇ , whereas those of Test Nos. 1 to 4 were reduced to about one-fifth of that of the conventional case. Potential level drift of Test Nos. 1 to 4 was found to be less than about one-fourth of that of the conventional case.
  • This example shows use of various cyclic compounds having at least one double bond and containing at least one nitrogen atom as water-keeping material, an inorganic salt and silver/silver iodide as an internal solid electrode.
  • Potassium ion selective electrodes were prepared in the same manner as in Example 18, except that the internal solid electrode was replaced with silver/silver iodide. The same intermediate layer, ion selective membrane, preparation and measurement procedures and evaluation items as in Example 18 were employed. Results of evaluation are shown in Table 18, where the water-keeping material used in Test Nos. 1 to 4 correspond to those of Chemical Formulas 1 to 4, respectively. Table 18 Test No. Electrode sensitivity (mV/dec.) Potential level drift (mV/20 hr) Electrode resistance (M ⁇ ) 1 58.5 8.9 21 2 58.2 9.3 18 3 56.5 7.6 20 4 57.5 7.9 19 Conventional 57.2 43 100
  • Electrode sensitivity to potassium ions of Test Nos. 1 to 4 including the conventional case was found to be about 56 to about 59 mV/dec. It was found that the electrode resistance of the conventional case was 100 M ⁇ , whereas those of Test Nos. 1 to 4 were reduced to about one-fifth of that of the conventional case. Potential level drift was found to be less than about one-fourth of that of the conventional case.
  • This example shows use of pyridine -2,5-carboxylic acid diethyl ether at various concentrations as a water-keeping material and silver/silver chloride as an internal solid electrode.
  • Potassium ion selective electrodes were prepared in the same manner as in Example 15, except that only pyridine-2,5-carboxylic acid diethyl ether of Chemical Formula 4 was used in ratios of 0.1, 0.5, 1.0, 2.0 and 5.0 to PVA by weight in Test Nos. 1 to 5, respectively, as a water-keeping material for the intermediate layer.
  • the same internal solid electrode, ion selective membrane, preparation and measurement procedures and evaluation items as in Example 15 were employed. Results of evaluation are shown in Table 19. Table 19 Test No.
  • Electrode sensitivity mV/dec.
  • Potential level drift mV/20 hr
  • Electrode resistance M ⁇ 1 0.1 57.7 25.2 52 2 0.5 57.3 25.0 31 3 1.0 58.1 9.6 19 4 2.0 57.1 10.5 19 5 5.0 56.9 11.2 20 Conventional - 57.1 51 220
  • Electrode sensitivity to potassium ions was found to be about 56 to about 59 mV/dec. throughout all the test numbers including the conventional case. Electrode resistance of the conventional case was found to be 220 M ⁇ , whereas it was found that those of Test No. 1 (ratio to PVA: 0.1 by weight) and Test No. 2 (ratio to PVA: 0.5 by weight) were reduced to about 50 and about 30 M ⁇ , respectively, and those of other test numbers were reduced to 20 M ⁇ or less, which was about one-tenth of that of the conventional case.
  • Potential level drifts of Test Nos. 1 and 2 were found to be a little as large as about 25 mV/2 hr, but those of other test numbers were reduced to less than about one-fifth of that of the conventional case.
  • This example shows use of pyridine-3-carboxylic acid at various concentrations as a water-keeping material and silver/silver chloride as an internal solid electrode.
  • Potassium ion selective electrodes were prepared in the same manner as in Example 15, except that only pyridine-3-carboxylic acid of Chemical Formula 3 was used in ratios to PVA of 0.1, 0.5, 1.0, 2.0 and 5.0 by weight as a water-keeping material for the intermediate layer.
  • the same internal solid electrode, ion selective membrane, preparation and measurement procedures and evaluation items as in Example 15 were employed. Results of evaluation are shown in Table 20. Table 20 Test No.
  • Electrode sensitivity mV/dec.
  • Potential level drift mV/20 hr
  • Electrode resistance M ⁇ 1 0.1 58.7 23.2 50 2 0.5 56.3 9.0 21 3 1.0 58.5 9.2 20 4 2.0 58.1 10.1 19 5 5.0 57.9 11.6 21 Conventional - 57.2 40 215
  • Electrode sensitivity to potassium ions was found to be about 56 to about 59 mV/dec. throughout all the test numbers including the conventional case. Electrode resistance of the conventional case was found to be 215 M ⁇ , whereas that of Test No. 1 (ratio: 0.1 by weight) was reduced to 50 M ⁇ , and those of Test Nos. 2 to 4 were reduced to 21 M ⁇ or less, which was about one-fourth of that of the conventional case. Potential level drift of Test No. 1 (ratio: 0.1 by weight) was a little as high as about 23 mV/20 hr, and those of Test Nos. 2 to 4 were reduced to about one-fourth of that of the conventional case.
  • This example shows use of pyridine-2,5-carboxylic acid diethyl ether as a water-keeping material, an inorganic salt at various concentrations and silver/silver chloride as an internal solid electrode.
  • Potassium ion selective electrodes were prepared in the same manner as in Example 15, except that only pyridine-2,5-carboxylic acid diethyl ether of Chemical Formula 4 was used in a ratio to PVA of 1.0 by weight as a water-keeping organic compound for the intermediate layer and potassium chloride was used as an inorganic salt in ratios to PVA of 0.1, 0.5, 1.0, 2.0 and 5.0 by weight (Test Nos. 1 to 5, respectively).
  • the same internal solid electrode, ion selective membrane, preparation and measurement procedures and evaluation items as Example 15 were employed. Results of evaluation are shown in Table 21. Table 21 Test No.
  • Electrode sensitivity mV/dec.
  • Potential level drift mV/20 hr
  • Electrode resistance M ⁇ 1 0.1 57.2 11.2 22 2 0.5 58.3 9.0 21 3 1.0 58.8 9.2 19 4 2.0 57.9 9.5 19 5 5.0 58.9 9.2 19 Conventional - 57.4 45 220
  • Electrode sensitivity to potassium ions was found to be about 56 to about 59 mV/dec. throughout all the test numbers including the conventional case. Electrode resistance of Test Nos. 1 to 5 was reduced to 22 M ⁇ or less, which was about one-tenth of that of the conventional case, irrespective of ratios of potassium chloride to PVA. Potential level drift of Test Nos. 1 to 5 was also reduced to about one-fourth of that of the conventional case, irrespective of ratios of potassium chloride to PVA.
  • This example shows evaluation of reproducibility when pyridine-2,5-carboxylic acid diethyl ether was used as a water-keeping material and silver/silver chloride was used as an internal solid electrode.
  • Potassium ion selective electrodes were prepared in the same manner as in Example 15, except that only pyridine-2,5-carboxylic acid diethyl ether of Chemical Formula 4 was used as a water-keeping organic compound for the intermediate layer.
  • the same internal solid electrode, ion selective membrane, intermediate layer composition and preparation method as in Example 15 were employed.
  • the thus prepared electrodes were subjected to determination of reproducibility, using aqueous potassium chloride solutions having different potassium ion concentrations (Test Nos. 1 to 3) as test solutions. Results of evaluation are shown in Table 22.
  • This examples shows evaluation of reproducibility when pyridine-2,5-carboxylic acid diethyl ether as a water-keeping material, an inorganic salt and silver/silver chloride as an internal solid electrode were used.
  • Potassium ion selective electrodes were prepared in the same manner as in Example 18, except that pyridine-2,5-carboxylic acid diethyl ether of Chemical Formula 4 as a water-keeping organic compound and potassium chloride as an inorganic salt were used each in a ratio to PVA of 1.0 by weight to prepare an intermediate layer, and subjected to determination of reproducibility, using aqueous potassium chloride solutions having different potassium ion concentrations (Test Nos. 1 to 3) as test solutions. The same internal solid electrode, ion selective membrane and preparation and measurement procedures as in Example 18 were employed. Results of evaluation are shown in Table 23. Table 23 Test No. Potassium ion concentration (mM) Number of measurements CV (%) as prepared Average of measurements 1 1.5 1.48 20 0.28 2 2.0 2.04 20 0.33 3 3.0 3.03 20 0.19
  • This example shows evaluation of reproducibility of field effect transistors.
  • Potassium ion sensitive, field effect transistors were prepared in the same manner as in Example 12, using one of the intermediate layers disclosed in Examples 15 to 25, and subjected to determination of reproducibility, using aqueous potassium chloride solutions having different potassium ion concentrations (Test Nos. 1 to 3) as test solutions. Results of evaluation are shown in Table 24.
  • Sodium ion selective electrodes and chloride ion selective electrodes could be prepared in the same manner as in Example 12 by replacing potassium chloride (KCl) with sodium chloride (NaCl) as an inorganic salt constituent for the intermediate layer and using a sodium selective membrane and chloride ion selective membrane, respectively, in place of the potassium ion selective membrane, and could have similar properties of electrode to those of the potassium ion selective electrodes.
  • KCl potassium chloride
  • NaCl sodium chloride
  • This example shows comparison of the present ion selective electrodes with a conventional one in changes in the electrode potential level in time course.
  • Fig. 6 is a diagram showing changes in the electrode potential level in time course when the present ion selective electrodes and a conventional one, as used in Example 15, were subjected to potassium ion measurement of an aqueous potassium chloride solution as a test solution, where results of electrode potential level measured at every intervals of 2 hours were plotted for every ten hours.
  • curve (c) shows changes in the electrode potential level of the conventional electrode without any intermediate layer, prepared in the same manner as in Example 15, in time course, when subjected to potassium ion measurement of an aqueous 100 mM potassium chloride solution as a test solution.
  • Curve (a) shows changes in the electrode potential level of an ion selective electrode of the present invention with an intermediate layer containing a water-keeping organic compound of Chemical Formula 1, prepared in the same manner as in Example 15, in time course
  • curve (b) shows those of another ion selective electrode of the present invention with an intermediate layer containing a water-keeping organic compound of Chemical Formula 3, prepared in the same manner as in Example 15, in time course.
  • the conventional ion selective electrode had a considerable decrease in the electrode potential level in time course, whereas the present ion selective electrodes had no substantial decrease in the electrode potential level in time course. This shows that a very stable equilibrium state was maintained between the ion selective membrane and the internal solid electrode of the present ion selective electrodes for a prolonged time.
  • This example shows comparison of the present ion selective electrodes with a conventional one in changes in the electrode potential level in time course.
  • Fig. 7 is a diagram showing changes in the electrode potential level in time course when the present ion selective electrodes, as used in Example 18, and a conventional electrode having the same composition as shown in Example 15, were subjected t potassium ion measurement of an aqueous potassium chloride solution as a test solution.
  • curve (c) shows changes in the electrode potential level of the conventional electrode without any intermediate layer, prepared in the same manner as in Example 15, in time course, when subjected to potassium ion measurement of an aqueous 100 mM potassium chloride solution as a test solution.
  • Curve (a) shows changes in the electrode potential level of an ion selective electrode of the present invention with an intermediate layer containing a water-keeping organic compound of Chemical Formula 2, prepared in the same manner as in Example 18, in time course and curve (b) shows those of another ion selective electrode of the present invention with an intermediate layer containing a water-keeping organic compound of Chemical Formula 4, prepared in the same manner as in Example 18, in time course.
  • the conventional ion selective electrode was rather unstable in changes in the electrode potential level in time course, showing a high drift, whereas the present ion selective electrodes were very stable in changes in the electrode potential level in time course, showing a less drift for a prolonged time than that of the conventional electrode.
  • the present ion sensor can have stable properties of electrode for a long time, as compared with the conventional one, and thus is more practical, and is particularly suitable for continuous measurement of liquid samples flowing along the path.
  • This example shows use of polyethylene gylcols having various molecular weights as a water-keeping material and silver/silver chloride as an internal solid electrode.
  • Example 2 Five potassium ion selective electrodes each with one of the following intermediate layers were prepared in the same manner as in Example 2, where intermediate layers containing one of polyethylene glycol (PEG) having a molecular weight of 200, 400, or 600 as water-keeping materials each in one of ratios of PEG to PVA of 0.1, 1.0, 2.0 and 5.0 by weight were employed. Intermediate layers containing one of PEGs in a ratio of PEG to PVA of 10.0 by weight were not practically available because mixed aqueous solutions containing one of PEGs and PVA were unstable and soon were separated into two phases, i.e. polyethylene glycol phase and water phase.
  • PEG polyethylene glycol
  • Each of the surfaces of these intermediate layers was pasted with the same ion selective membrane as in Example 1 to prepare potassium ion selective electrodes, which were subjected to measurement of changes in the electrode potential level in time course, using an aqueous 100 mM potassium chloride solution. Averages of drifts of electrode potential level of 5 electrodes for each molecular weight of PEGs for the time from the start of potential level measurement to 20 hours thereafter are shown in Table 25.
  • Potassium ion selective electrode with an intermediate layer containing PEG600 (molecular weight: 600) in a ratio to PVA of 2.0 by weight was found to have a minimum potential level drift.
  • This example shows use of an inorganic salt at various concentrations, polyethylene glycol as a water-keeping material and silver/silver chloride as an internal solid electrode.
  • Example 2 Five potassium ion selective electrodes each with one of the following intermediate layers were prepared in the same manner as in Example 2, where intermediate layers containing PEG600 (molecular weight: 600) as a water-keeping material and potassium chloride as an inorganic salt in one of ratios of KCl to PVA of 0.001, 0.01, 0.1, 1.0 and 2.0 by weight were employed. Each of the surfaces of these intermediate layers was then pasted with the same ion selective membrane as in Example 1 to prepare potassium ion selective electrodes, which were subjected to measurement of changes in the electrode potential level in time course, using an aqueous 100 mM potassium chloride solution.
  • PEG600 molecular weight: 600
  • potassium chloride as an inorganic salt in one of ratios of KCl to PVA of 0.001, 0.01, 0.1, 1.0 and 2.0 by weight were employed.
  • Each of the surfaces of these intermediate layers was then pasted with the same ion selective membrane as in Example 1 to prepare potassium ion selective electrodes, which were subjected to
  • This example shows use of polyethylene glycols having various molecular weights or ethylene glycol as water-keeping materials and silver/silver chloride as an internal solid electrode.
  • Chloride ion selective electrodes were prepared in the same manner as in Example 2, except that potassium chloride was replaced with sodium chloride, and a chloride ion selective membrane was used as an ion selective membrane, where one of intermediate layers containing ethylene glycol or polyethylene glycol (PEG) having a molecular weight of 200 or 600 in one of ratios to PVA of 0.1, 1.0, 2.0 and 5.0 by weight was used.
  • a chloride ion selective electrode with an intermediate layer composed only of PVA without any water-keeping material was prepared in the same manner as above to obtain reference data (blank data).
  • This example shows use of polyethylene glycol as a water-keeping material, an inorganic salt at various concentrations and silver/silver chloride as an internal solid electrode.
  • chloride ion selective electrodes each with one of the following intermediate layers were prepared in the same manner as in Example 2, except that sodium chloride was used as an inorganic salt, where polyethylene glycol (PEG) having a molecular weight of 600 was used as a water-keeping material for the intermediate layers in ratio to PVA of 2.0 by weight and sodium chloride was used as an inorganic salt in one of ratios to PVA of 0.01, 0.1, 1.0 and 2.0 by weight.
  • PEG polyethylene glycol
  • sodium chloride was used as an inorganic salt in one of ratios to PVA of 0.01, 0.1, 1.0 and 2.0 by weight.
  • the surfaces of the intermediate layers were then pasted with the same chloride ion selective electrode as in Example 31 to prepare chloride ion selective electrodes, which were subjected to measurement of changes in the electrode potential level in the same aqueous sodium chloride solution as in Example 31.

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US5856194A (en) 1996-09-19 1999-01-05 Abbott Laboratories Method for determination of item of interest in a sample
WO2005085827A1 (fr) * 2004-03-01 2005-09-15 Hach Company Electrodes selectives d'ions
WO2009095285A1 (fr) * 2008-01-28 2009-08-06 Robert Bosch Gmbh Élément de sonde pour sonde de gaz

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US5985117A (en) * 1997-12-29 1999-11-16 The Regents Of The University Of California Ion-selective membrane sensors with mercuracarborand ionophore
JP3625448B2 (ja) * 2002-01-11 2005-03-02 株式会社日立ハイテクノロジーズ イオンセンサ及びそれを用いた生化学自動分析装置
US20050067277A1 (en) * 2003-09-30 2005-03-31 Pierce Robin D. Low volume electrochemical biosensor
US20050191428A1 (en) * 2004-03-01 2005-09-01 Buck Michael D. Ion-selective electrodes
US7373195B2 (en) * 2004-07-30 2008-05-13 Medtronic, Inc. Ion sensor for long term use in complex medium
JP4331181B2 (ja) * 2006-03-30 2009-09-16 株式会社日立製作所 測定装置及び分析用素子
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WO2010045458A1 (fr) * 2008-10-15 2010-04-22 University Of Memphis Research Foundation Procédé et dispositif de détection d'une substance à analyser dans un échantillon de vapeur ou de gaz
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